I suspect it simply always shows the scan order (with a default value). I would trust the scan type.

You could test it. Play the DVD with MPC-HC. Assuming you are using LAV Video Decoder, access its settings and set "deinterlacing mode" to "disabled". Restart the player. If the video is interlaced, you should now be able to see it. Horizontal lines, mostly noticeable during fast moving scenes.